I am a bit worried about the temp!

Read here: https://www.backyardchickens.com/t/421122/think-its-too-cold-for-your-chickens-think-again

 

Ducks-love-me, the first post on that link is a response to someone worrying about relatively mild temperatures.

There are some things to consider:

How many animals. (the OP has 20 juvenile chickens - when they huddle together, the more birds, the warmer they can be)
How the individual flock behaves. (My runners sit nose-to-tail at most, have never huddled together, even when it's freezing.)
How individual birds behave. (Fünf and Sieben were quite sensitive to the cold the first year. Sieben has filled out, but not Fünf. She is still not very cold hardy)
Fire risk (Whatever you do, remember that electricity and bedding can make for a deadly fire.)
Smaller areas are easier to warm with body heat
Nice, thick (18 inches for example) dry as possible bedding really helps, as does cutting down drafts.
Well fed, well watered, healthy ducks can handle more extremes.
There are times when the weather just turns extremely cold, and having a ducky storm shelter may be a good idea. Ours became the night shelter, so that I don't have to make that judgment call - it will be warm enough. But not everyone has that option. Still, keeping a few ducks in the laundry room for one or two nights does not sound like a crisis to me.

If you have seen signs of them being too cold, try extra bedding, stacking straw bales around the perimeter of their shelter, covering the shelter with an extra tarp, things that insulate and reduce wind. But if you see their body condition declining, time to change strategy.

 

Did not read all responses, but I read your original post quickly. Above all, make sure they have water that does not freeze and they can dunk faces/nares/eyes in. You can set out flat pans of water for bathing. Mine have a pool with bird bath heater and I fill individual pans with HOT water during day (dumped at night). Mine eat a combo of crumbles and pellets, chopped veggies (romaine, arugula, chard, dandelion greens, etc, with chopped green pepper and/or tomato), cracked corn, some crunched up cat food, and peas. Always with thawed water. It was almost -15 last night and they all seemed ok in the am. They have a place to get out of the elements, which is key.
I use straw not hay, it has more insulating properties and will not pack down when wet or pooped on. Plus mine LOVE the seeds in it.
Hope some or all of this helps. Gotta go check my kids!!